A World to Explore

Archive for June, 2015

I spent 25 days in England, Scotland and Wales this month, 12 of them with these two happy Senior Independent Study students, Mae Kemsley (’16) and Meredith Mann (’16) — dubbed “Team Yorkshire”. We had to delay our blog posts until today. You can see all of them by clicking the UK2015 tag. It was a spectacular expedition. Thanks again to Paul Taylor, Jen Loxton, Joanne Porter, Tim Palmer, Patrice Reeder and Suzanne Easterling for the parts they played in this adventure. Thank you as well to Mae and Meredith who were not only sharp field paleontologists, they were great companions as well. They are shown above on the tip of Filey Brigg in North Yorkshire. (N54.21560°, W00.25842°; Google Earth image below. Cool study site!)

As one of the most militarized islands, because of the dispute between Japan and Russia (the Kuril Islands dispute), Shikotan Island has remained a mystery to the world of tree rings and climate studies until now.

Shikotan Island directly on the margin between the Pacific and Eurasian Plates. This special location indicates that this island is greatly influenced by geological factors, such as tsunami, earthquake, and large changes in climate (see photos below).

Figure 2. Big crack after the Shikotan Island earthquake of 1994.

Figure 3. Shikotan Island surrounded by sea ice (Wikipedia).

In order to better define the climate history of the Island in 2014 Russian geologist E. Dolgova and M. Alexandrin collected core samples from larch, spruce and fir trees on Shikotan islands.

Figure 4. Location of collection sites of all Shikotan cores. The island is approximately 30 km long (image from GooglEarth).

The purpose of this research is to find the climate information from these cores. These cores are properly sanded and marked. Forty six cores were collected from Shikotan Island and 20 were used to construct the chronology for this island.

Figure 5. Family picture of all cores in the chronology

As we can see, some cores are less than 100 years old and some cores can be dated back to 18th century. Despite the age difference these 20 cores correlate with each other well.The purpose of this research is to extract climate information from these cores. These cores are properly sanded and marked by year. Forty six cores were collected from Shikotan Island and 20 were used to construct the chronology for this island.

The tree ring width can be influenced by various factors other than climate signal, such as the growth trends and natural competition. The growth trends is the major factor that we want to eliminate. The above picture shows us the standardized tree ring measurements by removing the growth trends. The blue line is the sample size. This is the first tree-ring record from Shikotan Island.

The standardized ring width chronology has a slight downward trend since 1900. I compared the standardized tree ring data with the meteorological data from Nemuro station (130 years long). It appears that September temperature has a strong negative correlation with the tree ring width. The correlation is 0.43, which is far above the 99% confidence level. The reason for such negative correlation is unknown, however, it may be related to changes in sea ice extent.

In addition to examining the correlation between ring width and temperature, I focused on the possible relationship between tree ring width and natural hazards, such as tsunami and earthquake.

After looking at the tsunami occurrence data from NOAA, I found that sometimes tsunami corresponded with a year of rapid growth. For example, in 1963, there are two tsunamis on Shikotan Island and some cores has a bigger growth this year compared to the year before. Photos below are two cores that show the correlation with the tsunami record and there are more cores have a correlation with the tsunami record. This relationship is under investigation.

BRISTOL, ENGLAND (June 26, 2015) — Tim Palmer has a professional interest in building stones, and a passion for sorting out their characteristics and historical uses. He thus has many contacts in the stone industry, from architects to quarry managers. This morning we visited the Doulting Stone Quarry on the outskirts of Doulting near Shepton Mallet in Somerset. Here a distinctive facies of the Jurassic Inferior Oolite is excavated for a variety of purposes. The rock has a lovely color, is relatively easy to work, and is durable. Above is a quarry saw that cuts out huge blocks from the natural exposure.

Such sawing produces great cross-sections for geologists to examine. We were particularly interested in that light-colored unit above with the irregular top and dark sediment-filled holes. The holes are part of a network of Thalassinoides burrows (tunnels made by Jurassic crustaceans) and reduce the value of the rock as a building stone. There is thus lots of it laying around the quarry yard for study.

One impressive fossil exposed by the sawing is this pinnid bivalve, probably Trichites.

The Thalassinoides burrows are filled with a poorly-cemented sediment. It is full of little fossils, so we collected a bag of it for microscopic examination. It may give us clues as to what communities lived on the surface of this burrowed unit when it was part of the Jurassic seafloor.

We had a tour of the quarry shops, which included seeing these giant rock saws in action. Many of the saws are controlled by computers, so elaborate cuts can be made.

This rock has been quarried since Roman times, so there is over 2000 years of stone working here. The quarry owner set aside this rock face which shows chisel marks made in Medieval times. Wooden wedges were jammed into chiseled channels and then pulled over days to eventually crack the stone free.

After the quarry visit, Tim Palmer and I tromped through the woods and eventually found (with the help of several locals) an exposure known as Tedbury Camp. It is another Jurassic-on-Carboniferous unconformity like we saw at Ogmore-By-Sea earlier in the week. A century ago quarry workers cleared off this surface of Carboniferous limestone. It is a wave-cut platform on which Jurassic sediments (the Inferior Oolite) were deposited. The surface has many geological delights, including faults, drag folds, differentially-weathered cherts and carbonates, and Jurassic borings and encrusters. Beautiful.

In this view of the surface you may be able to see the odd folding of the dark chert layers in the right middle of the image. These seem to be drag folds along a fault. They clearly predate the Jurassic erosion of the limestone surface. The overlying Jurassic can be seen in the small outcrop on the left near Tim.

In this cross-section of the erosional surface you can clearly see we’re working with an angular unconformity.

Trypanites borings are abundant across this surface, most filled with lighter Jurassic sediment. There are other borings here too that deviate from the straight, cylindrical nature of Trypanites.

I don’t know yet how to classify these curved borings. They resemble Palaeosabella.

Here is a Jurassic bivalve attached to the Carboniferous limestone at the unconformity. Most of the encrusters have been eroded away.

There are many possibilities for further study of the Tedbury Camp unconformity. This was a productive site for our last field visit in England this year. Thank you very much to Tim Palmer, seated above, for his expertise, great companionship, and generosity with his time. It was a reminder of how much fun we had together in the field twenty years ago.

My month of geology in the United Kingdom has now come to an end. My next two days will be devoted to packing up and making the long train and then plane flights home. What a wonderful time I had, as did my students on the earlier part of the trip, Mae Kemsley and Meredith Mann. Thank you again to Paul Taylor for his work with us in Scarborough. I am very fortunate with my fine British friends.

I love this kind of fossil, which explains why you’ve seen so many examples on this blog. We are looking at an encrusted external mold of the bivalve Anomalodonta gigantea found in the Waynesville Formation exposed in Franklin County, Indiana. I collected it many years ago as part of an ongoing study of this kind of preservation and encrustation.To tell this story, I’ve lettered the primary interest areas on image above. First, an external mold is an impression of the exterior of an organism. In this case we have a triangular clam with radiating ribs in its shell. The exterior of the shell with its ribs was buried in sediment and the shell dissolved, leaving the basic impression above. It is a negative relief. Please now refer to the letters for the close-up images below.

A. At the distal end of the bivalve mold is what looks at first to be the original shell. It is calcitic, though, and we know this bivalve had an aragonitic shell. A closer look shows that this is actually the attaching surface of an encrusting bryozoan that bioimmured the original bivalve shell, which has since dissolved away. This smooth surface is the bryozoan underside; we see the characteristic zooecia (tubes holding the individual zooids) only when this surface is weathered away.

B. These tubular objects are infillings of borings (maybe Trypanites)that were cut into the original aragonitic shell of the bivalve. The tunnels of the borings were filled with fine sediment, and then the shell dissolved away, leaving these casts of the borings.

C and D. In the middle of the external mold is this curious circular feature (C) mostly surrounded by a bryozoan (D). There was at one time a circular encruster, likely an inarticulate brachiopod like Petrocrania, that sat directly on the external mold surface. The bryozoan colony grew around but not over it because it was alive and still opening and closing its valves for feeding. The bryozoan built a vertical sheet of skeleton around it as a kind of sanitary wall. You may be able to see the other three or four structures in the top image showing brachiopod encrusters that left the building. This is an example of fossils showing us a living relationship, even if one is not longer preserved.

This fossil and its sclerobionts (hard substrate dwellers) show us that soon after the bivalve died its aragonitic shell dissolved away, leaving as evidence the external mold in the sediment, the bioimmuring bryozoan, and the boring casts. Very soon thereafter bryozoans and brachiopods encrusted the available hard substrate. This is a typical example of early aragonite dissolution on the sea floor during a Calcite Sea interval.

BRISTOL, ENGLAND (June 25, 2015) — Our little geological exploration of southern Britain now passes into England. Tim Palmer and I crossed the River Severn and drove to the Cotswolds to examine old quarry exposures and Medieval stonework. We are parked above in Salterley Quarry near Leckhampton Hill.

Our theme again is Jurassic. At Leckhampton Hill we examined exposures of the Middle Jurassic Inferior Oolite. It is not, of course, inferior to anything in the modern sense. The name, originally from William Smith himself, refers to its position below the Great Oolite. This is Devil’s Chimney, a remnant of stone left from quarrying in the 19th Century.

We stopped along a bend in a Cotswold road called Fiddler’s Elbow and found an old carbonate hardground friend in the Inferior Oolite. Borings are evident in this flat, eroded surface. Next to the hammer are pieces of the Pea Grit, a coarser facies. I want to examine the grains for microborings and encrusters.

This is the gorgeous dog-rose (Rosa canina, not surprisingly), which is common in the Cotswolds. It is the model for the Tudor Rose in heraldry.

These tall orchids were also abundant near our outcrops.

A closer view of the orchids. When I learn the name for this plant, I’ll amend this post. [And we have one! Caroline Palmer identified the flowers as Dactylorhiza sp. Thanks, Caroline!]

At the end of the day we stopped by St. Mary’s Church in Painswick, with its distinctive churchyard and variety of building stones. The sculptured trees are English yews.

The gravestones date back to the early 18th Century, with older ledger stones inside the church.

The unique pyramidal tomb of the stonemason John Bryan (1716-1787). He was apparently responsible for most of the 18th Century ornate monuments in this churchyard.

Many of the gravestones have copper plates affixed to their upper faces. The rain washes copper ions out of the metal and over the limestone, killing the lichens and other encrusting organisms. This leaves the lighter patch of bare limestone. Somewhere in this is a study of microbiome ecological gradients!

The Painswick church was the site of a 1643 battle during the English Civil War. There are numerous bullet and shot marks on the exterior stones. Tim commented on the remarkable resilience of this stone to stay coherent after almost 400 years of weathering of these pits.

BRIDGEND, WALES (June 25, 2015) — On our last day in Wales, Tim had an errand at the National Museum Wales in Cardiff. We took the opportunity to visit their new dinosaur exhibit with the skeleton that had been collected from an outcrop we visited earlier in the week at Lavernock Point.

The exhibit is well done. The fossil skeleton represents the first carnivorous dinosaur found in Wales, and one of the earliest Jurassic dinosaurs found anywhere.

Here are some of the bones in lower Lias limestone.

This is a museum photo of the dinosaur collecting site. You may recognize the place from a previous post in this blog.

This is Cardiff City Hall. I loved the early 20th Century architecture in this Cardiff district, but we didn’t have time to explore. It is now off to southern England for more fieldwork.

BRIDGEND, WALES (June 24, 2015) — Today Tim Palmer and I visited a famous unconformable rock plane in South Wales. I last saw it thirty years ago, when I knew a lot less about eroded, bored and encrusted surfaces. It is an unconformity between a Carboniferous limestone (High Tor Limestone, Dinantian in age) and an overlying Jurassic limestone (Sutton Stone, Hettangian, Lower Jurassic) exposed on the coast near Ogmore-By-Sea. It was most thoroughly described in 2004 by Johnson and McKerrow (Palaeontology 38: 529-541). You can see it as the surface above, with the Jurassic rocks on top of it to the right. (I know, gray rocks on gray rocks. It takes close examination to tell them apart after they both have been subjected to coastal weathering.)

Here is a closer view with part of the Lower Jurassic Sutton Stone broken away to show fresh material. (We didn’t do this, despite the guilty-looking hammer. The hammer is Paul Taylor’s, by the way. Thanks, Paul!) Note the pebbles in the Sutton Stone. They are made of the Carboniferous limestone beneath. Classic unconformity.

The Carboniferous limestone is punctured by numerous small borings (Trypanites) drilled by filter-feeding worms of some kind when the Early Jurassic sea covered this surface. They are the clusters of small black dots shown above.

In this closer view of the borings you can see that they are filled with a lighter Jurassic sediment. The openings have been somewhat enlarged by weathering.

This erosion surface shows some relief, probably formed by cobbles and pebbles washing over it during the Early Jurassic. This matches what we see on modern wave-cut rocky platforms.

On the same stretch of shoreline there is a small section where Triassic wadi deposits cut down into the Carboniferous limestone — another even more dramatic unconformity, but without marine fossils.

Coming from a desert myself, I have an affinity for wadi sediments. They are coarse, angular and poorly sorted. These grains are entirely from the underlying Carboniferous limestone. They were likely generated from steep rocky canyons through which intermittent streams flowed.

At the end of the day Tim and I visited Nash Point, again on the coast of South Wales. Here the Lias is brilliantly (and dangerously!) exposed as a series of alternating limestones and shales.

We didn’t get too close to these unstable cliffs. The limestone blocks fall often as the interbedded soft shales holding them in place weather away.

A view of Nash Point at low tide. Tim always wears that red jacket, so he’s easy to spot. (Classic Redcoat!)

We didn’t find much to paleontologically interest us at this last outcrop, but it was beautiful on another stunning coastal day. These cobbles, all made of Lias limestones, are pretty to look at, but tiresome to walk through. We were ready for a slow dinner after this excellent day.

BRIDGEND, WALES (June 23, 2015) — My train journey yesterday was successful. It was close, but I made the four tight connections and arrived in Aberystwyth, Wales, from Thurso, Scotland, on schedule. It took 15 hours. My friend Tim Palmer was there to greet me as I stumbled out of my carriage. I went from rainy, cold Scotland to warm and sunny Wales. The top image is of the Triassic/Jurassic transition at Lavernock Point in south Wales (see below).

My first Welsh night was with Tim in his great country home (with is wife Caroline) on the outskirts of Aberystwyth. It is called The Old Laundry because of its function on a previous manorial estate. I had my best sleep here for the entire trip. Quiet and beautiful.

One of Tim’s passions is the study of building stones in England and Wales. As we drove to southern Wales for our geological work, we stopped by interesting stone structures, including the ruins of Talley Abbey, a 12th Century monastery.

Tim is here examining the dressing stones on a corner of this pillar in the Talley Abbey ruins. I learned that these dressings are usually made of stone that can be easily shaped, is attractive, and will hold sharp edges. In many cases these are called “freestones”.

Our first geological stop was at Lavernock Point on the southern coast of Wales. We looked here at the boundary section between the Upper Triassic and Lower Jurassic (Lias). In this view we see an alternating sequence of limestones (buff-colored) and shales (dark gray) of the lower Lias. These are marginal marine units with oysters and ammonites. On the left side of the image you can see a broad niche cut back into the cliff. This is the site where the first carnivorous dinosaur in Wales was recently excavated. It is also one of the oldest Jurassic dinosaurs since it was discovered just above the Triassic/Jurassic boundary. More on this dinosaur later.

We wandered across broad intertidal wave-cut platforms at Lavernock Point looking at the limestones and shales of the lower Lias. I was intrigued by these features on some bedding planes. They are not desiccation cracks, but rather some combination of jointing and weathering.

The oyster Liostrea hisingeri is very common in this part of the Lias. In the limestones it is sectioned by erosion, resulting in these shelly outlines.

When Liostrea hisingeri is present in the shales, it is preserved three dimensionally.

After our geologizing was done for the day, Tim and I drove up into the Rhondda Valleys just north of our hotel. This was at one time a very busy coal mining and industrial region, but the mines are closed and most of the heavy industry has moved elsewhere. Above is a view down a street in Tonypandy, one of the more famous towns of The Valleys. There were massive riots here in 1910 which eventually a minimum wage for miners in 1912.

THURSO, SCOTLAND (June 22, 2015) — Back to the trains today as I leave for a long journey south through Scotland and central England and then west to Aberystwyth, Wales, to spend some quality field time with my friend Tim Palmer. Our goal will be to explore sites for potential Independent Study projects.

Lots of time on the trains coming up on this trek. Even more if I miss a connection. British train journeys often include only a few minutes to change trains at a station. This is not always a straightforward task.

The tracks at Thurso are the most northerly extension of the British rail system.

STROMNESS, SCOTLAND (June 21, 2015) — I intended to explore the region around Stromness today as I waited for the late afternoon ferry to Thurso, but it rained continuously. Since I can’t afford to get my meager kit wet while traveling, I was confined to indoors activities, including visiting the excellent though small Stromness Museum.

The bulk of the museum displays are devoted to maritime history, naturally, but there is always some geology. This, for example, is a beautiful piece of labradorite (from, naturally, Labrador) used as ship ballast.

I was very pleased to see this small exhibit on the brilliant polymath Hugh Miller (1802-1856) and the fossils he collected from Devonian rocks in the region. This is his most famous specimen: “The Asterolepis of Stromness”. He was the earliest expert on the Old Red Sandstone and its fossils.

This afternoon I take the ferry across these stormy seas back to the Scottish mainland. I’ve very much enjoyed Orkney, cold and wet though it is.